When trucks having a frame which is rigid from the cab to the bed has heavy loads thereon, the rear end of the truck will go down and the front end of the truck will go up, thereby defeating a major purpose of the suspension system and creating an unstable vehicle. For this reason, many heavy suspension systems are produced at a considerable expense and also many vehicles have expensive overload spring structures attached thereto for the few times that the vehicle may have a very heavy load thereon.
U.S. Pat. No. 3,069,149 shows one form of auxiliary overload structure including a pair of rubber bumpers that bump together when the suspension coil springs have been overly compressed due to a very heavy load. This structure is not entirely satisfactory because when the rubber bumpers are together and the vehicle hits a bump, there is very little spring action in the rubber bumpers to resist the shock of such a bump.
U.S. Pat. No. 3,850,444 to Wright shows another overload spring arrangement, but it merely adds an additional spring element basically equivalent to adding another heavier coil spring to the suspension system rather than providing a way to modify the behavior of the suspension springs already present in the original equipment on the vehicle.
Accordingly, there is a need for a suspension system attachment to automatically redistribute the load from rear to front when under heavy load conditions.